i’m facing following error when starting up the application with Oracle database, this happens after upgraded the spring from 2.x to 3.x, which upgraded the hibernate from 5.x to 6.x.

2024-05-08 16:49:43,551 +08:00 ERROR LocalContainerEntityManagerFactoryBean [main] - Failed to initialize JPA EntityManagerFactory: [PersistenceUnit: fooBar] Unable to build Hibernate SessionFactory; nested exception is org.hibernate.MappingException: Could not instantiate id generator [entity-name=x.y.z.Foo]

Following is my entity class structure

@Entity
public class Foo implements Serializable
{
    @Id
    @SequenceGenerator(name = "FooSeqGenerator", sequenceName = "Foo_Seq")
    @GeneratedValue(strategy = GenerationType.AUTO, generator = "FooSeqGenerator")
    private int id;
    private String name;
}

Following is my sequence

CREATE SEQUENCE Foo_Seq INCREMENT BY 1 MINVALUE 1 MAXVALUE 9999999999999999999999999999 NOCYCLE CACHE 20 NOORDER

This problem resolved after i overrided the allocationSize attribute in SequenceGenerator annotation as follows

@SequenceGenerator(name = "FooSeqGenerator", sequenceName = "Foo_Seq", allocationSize = 1)

But i don’t understand why this error occurred & why this change fixed the problem. Can anyone explain this? Or what should i do to fix this problem? Thanks.